Add support for user defined handlers

# Details

Allow users to specify handlers for whatever language they want
using the `custom_handlers` configuration parameter.

As an implementation it is meant to give users the same ability
as the native renderers for `markdown`, `markdown_inline` and
`latex`. Convenience methods are not provided and users are
expected to use the vim api directly.

Provide an example as well as some details in the README.

By integrating with this plugin the `extmarks` set by the user
will behave identically to the ones created by the plugin. All
validation on buffers, windows and state also works as expected.

Author: MeanderingProgrammer

README.md

@@ -20,6 +20,7 @@ Plugin to improve viewing Markdown files in Neovim
 - Basic support for `LaTeX` if `pylatexenc` is installed on system
 - Disable rendering when file is larger than provided value
 - Support for [callouts](https://github.com/orgs/community/discussions/16925)
+- Support custom handlers which are ran identically to native handlers
 
 # Dependencies
 
@@ -149,6 +150,9 @@ require('render-markdown').setup({
     --  normal: renders the rows of tables
     --  none: disables rendering, use this if you prefer having cell highlights
     table_style = 'full',
+    -- Mapping from treesitter language to user defined handlers
+    -- See 'Custom Handlers' section for more info
+    custom_handlers = {},
     -- Define the highlight groups to use when rendering various components
     highlights = {
         heading = {
@@ -204,6 +208,73 @@ require('render-markdown').setup({
 
 - Function can also be accessed directly through `require('render-markdown').toggle()`
 
+# Custom Handlers
+
+Custom handlers allow users to integrate custom rendering for either unsupported
+languages or to override the native implementations. This can also be used to
+disable a native language, as custom handlers have priority.
+
+For example disabling the `LaTeX` handler can be done with:
+
+```lua
+require('render-markdown').setup({
+    custom_handlers = {
+        latex = { render = function() end },
+    },
+}
+```
+
+Each handler must conform to the following interface:
+
+```lua
+---@class render.md.Handler
+---@field public render fun(namespace: integer, root: TSNode, buf: integer)
+```
+
+The `render` function parameters are:
+
+- `namespace`: The id that this plugin interacts with when setting and clearing `extmark`s
+- `root`: The root treesitter node for the specified language
+- `buf`: The buffer containing the root node
+
+Custom handlers are ran identically to native ones, so by writing custom `extmark`s
+(see :h nvim_buf_set_extmark()) to the provided `namespace` this plugin will handle
+clearing the `extmark`s on mode changes as well as re-calling the `render` function
+when needed.
+
+This is a high level interface, as such creating, parsing, and iterating through
+a treesitter query is entirely up to the user if the functionality they want needs
+this. We do not provide any convenience functions, but you are more than welcome
+to use patterns from the native handlers.
+
+## More Complex Example
+
+Lets say for `python` we want to highlight lines with function definitions.
+
+```lua
+-- Parse query outside of the render function to avoid doing it for each call
+local query = vim.treesitter.query.parse('python', '(function_definition) @def')
+local function render_python(namespace, root, buf)
+    for id, node in query:iter_captures(root, buf) do
+        local capture = query.captures[id]
+        local start_row, _, _, _ = node:range()
+        if capture == 'def' then
+            vim.api.nvim_buf_set_extmark(buf, namespace, start_row, 0, {
+                end_row = start_row + 1,
+                end_col = 0,
+                hl_group = 'DiffDelete',
+                hl_eol = true,
+            })
+        end
+    end
+end
+require('render-markdown').setup({
+    custom_handlers = {
+        python = { render = render_python },
+    },
+}
+```
+
 # Purpose
 
 There are many existing markdown rendering plugins in the Neovim ecosystem. However,

doc/render-markdown.txt

@@ -1,4 +1,4 @@
-*render-markdown.txt*            For 0.10.0           Last change: 2024 May 22
+*render-markdown.txt*            For 0.10.0           Last change: 2024 May 31
 
 ==============================================================================
 Table of Contents                          *render-markdown-table-of-contents*
@@ -11,12 +11,14 @@ Table of Contents                          *render-markdown-table-of-contents*
   - packer.nvim                          |render-markdown-install-packer.nvim|
 5. Setup                                               |render-markdown-setup|
 6. Commands                                         |render-markdown-commands|
-7. Purpose                                           |render-markdown-purpose|
-8. Markdown Ecosystem                     |render-markdown-markdown-ecosystem|
+7. Custom Handlers                           |render-markdown-custom-handlers|
+  - More Complex Example|render-markdown-custom-handlers-more-complex-example|
+8. Purpose                                           |render-markdown-purpose|
+9. Markdown Ecosystem                     |render-markdown-markdown-ecosystem|
   - Render in Neovim     |render-markdown-markdown-ecosystem-render-in-neovim|
   - Render in Browser   |render-markdown-markdown-ecosystem-render-in-browser|
   - Orthogonal                 |render-markdown-markdown-ecosystem-orthogonal|
-9. Links                                               |render-markdown-links|
+10. Links                                              |render-markdown-links|
 
 ==============================================================================
 1. markdown.nvim                               *render-markdown-markdown.nvim*
@@ -41,6 +43,7 @@ Plugin to improve viewing Markdown files in Neovim
 - Basic support for `LaTeX` if `pylatexenc` is installed on system
 - Disable rendering when file is larger than provided value
 - Support for callouts <https://github.com/orgs/community/discussions/16925>
+- Support custom handlers which are ran identically to native handlers
 
 
 ==============================================================================
@@ -178,6 +181,9 @@ modified by the user.
         --  normal: renders the rows of tables
         --  none: disables rendering, use this if you prefer having cell highlights
         table_style = 'full',
+        -- Mapping from treesitter language to user defined handlers
+        -- See 'Custom Handlers' section for more info
+        custom_handlers = {},
         -- Define the highlight groups to use when rendering various components
         highlights = {
             heading = {
@@ -237,7 +243,77 @@ modified by the user.
 
 
 ==============================================================================
-7. Purpose                                           *render-markdown-purpose*
+7. Custom Handlers                           *render-markdown-custom-handlers*
+
+Custom handlers allow users to integrate custom rendering for either
+unsupported languages or to override the native implementations. This can also
+be used to disable a native language, as custom handlers have priority.
+
+For example disabling the `LaTeX` handler can be done with:
+
+>lua
+    require('render-markdown').setup({
+        custom_handlers = {
+            latex = { render = function() end },
+        },
+    }
+<
+
+Each handler must conform to the following interface:
+
+>lua
+    ---@class render.md.Handler
+    ---@field public render fun(namespace: integer, root: TSNode, buf: integer)
+<
+
+The `render` function parameters are:
+
+- `namespace`: The id that this plugin interacts with when setting and clearing `extmark`s
+- `root`: The root treesitter node for the specified language
+- `buf`: The buffer containing the root node
+
+Custom handlers are ran identically to native ones, so by writing custom
+`extmark`s (see :h nvim_buf_set_extmark()) to the provided `namespace` this
+plugin will handle clearing the `extmark`s on mode changes as well as
+re-calling the `render` function when needed.
+
+This is a high level interface, as such creating, parsing, and iterating
+through a treesitter query is entirely up to the user if the functionality they
+want needs this. We do not provide any convenience functions, but you are more
+than welcome to use patterns from the native handlers.
+
+
+MORE COMPLEX EXAMPLE    *render-markdown-custom-handlers-more-complex-example*
+
+Lets say for `python` we want to highlight lines with function definitions.
+
+>lua
+    -- Parse query outside of the render function to avoid doing it for each call
+    local query = vim.treesitter.query.parse('python', '(function_definition) @def')
+    local function render_python(namespace, root, buf)
+        for id, node in query:iter_captures(root, buf) do
+            local capture = query.captures[id]
+            local start_row, _, _, _ = node:range()
+            if capture == 'def' then
+                vim.api.nvim_buf_set_extmark(buf, namespace, start_row, 0, {
+                    end_row = start_row + 1,
+                    end_col = 0,
+                    hl_group = 'DiffDelete',
+                    hl_eol = true,
+                })
+            end
+        end
+    end
+    require('render-markdown').setup({
+        custom_handlers = {
+            python = { render = render_python },
+        },
+    }
+<
+
+
+==============================================================================
+8. Purpose                                           *render-markdown-purpose*
 
 There are many existing markdown rendering plugins in the Neovim ecosystem.
 However, most of these rely on syncing a separate browser window with the
@@ -254,7 +330,7 @@ this plugin.
 
 
 ==============================================================================
-8. Markdown Ecosystem                     *render-markdown-markdown-ecosystem*
+9. Markdown Ecosystem                     *render-markdown-markdown-ecosystem*
 
 There are many `markdown` plugins that specialize in different aspects of
 interacting with `markdown` files. This plugin specializes in rendering the
@@ -297,7 +373,7 @@ also have no issues running alongside this plugin.
     specific keybindings for interacting with `markdown` files
 
 ==============================================================================
-9. Links                                               *render-markdown-links*
+10. Links                                              *render-markdown-links*
 
 1. *Demo*: demo/demo.gif
 

lua/render-markdown/handler/latex.lua

@@ -11,7 +11,7 @@ local cache = {
 
 local M = {}
 
----@param namespace number
+---@param namespace integer
 ---@param root TSNode
 ---@param buf integer
 M.render = function(namespace, root, buf)

lua/render-markdown/handler/markdown.lua

@@ -5,7 +5,7 @@ local util = require('render-markdown.util')
 
 local M = {}
 
----@param namespace number
+---@param namespace integer
 ---@param root TSNode
 ---@param buf integer
 M.render = function(namespace, root, buf)

lua/render-markdown/handler/markdown_inline.lua

@@ -3,7 +3,7 @@ local state = require('render-markdown.state')
 
 local M = {}
 
----@param namespace number
+---@param namespace integer
 ---@param root TSNode
 ---@param buf integer
 M.render = function(namespace, root, buf)

lua/render-markdown/health.lua

@@ -40,7 +40,10 @@ local function check_keys(t1, t2, path)
         elseif type(v1) ~= type(v2) then
             table.insert(errors, string.format('Invalid type: %s, expected %s but found %s', key, type(v1), type(v2)))
         elseif type(v1) == 'table' and type(v2) == 'table' then
-            vim.list_extend(errors, check_keys(v1, v2, key_path))
+            -- Some tables are meant to have unrestricted keys
+            if k ~= 'custom_handlers' then
+                vim.list_extend(errors, check_keys(v1, v2, key_path))
+            end
         end
     end
     return errors

lua/render-markdown/init.lua

@@ -34,6 +34,9 @@ local M = {}
 ---@field public quote? string
 ---@field public callout? render.md.UserCallout
 
+---@class render.md.Handler
+---@field public render fun(namespace: integer, root: TSNode, buf: integer)
+
 ---@class render.md.UserConceal
 ---@field public default? integer
 ---@field public rendered? integer
@@ -58,6 +61,7 @@ local M = {}
 ---@field public callout? render.md.UserCallout
 ---@field public conceal? render.md.UserConceal
 ---@field public table_style? 'full'|'normal'|'none'
+---@field public custom_handlers? table<string, render.md.Handler>
 ---@field public highlights? render.md.UserHighlights
 
 ---@type render.md.Config
@@ -147,6 +151,9 @@ M.default_config = {
     --  normal: renders the rows of tables
     --  none: disables rendering, use this if you prefer having cell highlights
     table_style = 'full',
+    -- Mapping from treesitter language to user defined handlers
+    -- See 'Custom Handlers' section for more info
+    custom_handlers = {},
     -- Define the highlight groups to use when rendering various components
     highlights = {
         heading = {

lua/render-markdown/types.lua

@@ -52,4 +52,5 @@
 ---@field public callout render.md.Callout
 ---@field public conceal render.md.Conceal
 ---@field public table_style 'full'|'normal'|'none'
+---@field public custom_handlers table<string, render.md.Handler>
 ---@field public highlights render.md.Highlights

lua/render-markdown/ui.lua

@@ -33,14 +33,20 @@ M.refresh = function(buf)
     parser:for_each_tree(function(tree, language_tree)
         local language = language_tree:lang()
         logger.debug({ language = language })
-        if language == 'markdown' then
-            markdown.render(M.namespace, tree:root(), buf)
-        elseif language == 'markdown_inline' then
-            markdown_inline.render(M.namespace, tree:root(), buf)
-        elseif language == 'latex' then
-            latex.render(M.namespace, tree:root(), buf)
+        local user_handler = state.config.custom_handlers[language]
+        if user_handler == nil then
+            if language == 'markdown' then
+                markdown.render(M.namespace, tree:root(), buf)
+            elseif language == 'markdown_inline' then
+                markdown_inline.render(M.namespace, tree:root(), buf)
+            elseif language == 'latex' then
+                latex.render(M.namespace, tree:root(), buf)
+            else
+                logger.debug('No handler found')
+            end
         else
-            logger.debug('No handler found')
+            logger.debug('Using user defined handler')
+            user_handler.render(M.namespace, tree:root(), buf)
         end
     end)
     logger.flush()

scripts/update.py

@@ -10,18 +10,34 @@ def main() -> None:
 
 
 def update_types(init_file: Path) -> None:
-    lines: list[str] = []
+    # Group comments into class + fields
+    lua_classes: list[list[str]] = []
+    current_class: list[str] = []
     for comment in get_comments(init_file):
         comment_type: str = comment.split()[0].split("@")[-1]
-        if comment_type in ["class", "field"]:
-            comment = comment.replace("User", "")
-            if comment_type == "field":
-                assert "?" in comment, f"All fields must be optional: {comment}"
-                comment = comment.replace("?", "")
-            if comment_type == "class" and len(lines) > 0:
-                lines.append("")
-            lines.append(comment)
-    lines.append("")
+        if comment_type == "class":
+            if len(current_class) > 0:
+                lua_classes.append(current_class)
+            current_class = [comment]
+        elif comment_type == "field":
+            current_class.append(comment)
+    lua_classes.append(current_class)
+
+    # Generate lines that get written to types.lua
+    lines: list[str] = []
+    for lua_class in lua_classes:
+        name, fields = lua_class[0], lua_class[1:]
+        if "User" in name:
+            # User classes are expected to have optional fields
+            lines.append(name.replace("User", ""))
+            for field in fields:
+                assert "?" in field, f"User fields must be optional: {field}"
+                lines.append(field.replace("User", "").replace("?", ""))
+            lines.append("")
+        else:
+            # Non user classes are expected to have mandatory fields
+            for field in fields:
+                assert "?" not in field, f"Non user fields must be mandatory: {field}"
 
     types_file: Path = Path("lua/render-markdown/types.lua")
     types_file.write_text("\n".join(lines))
@@ -62,9 +78,9 @@ def get_default_config(file: Path) -> str:
 def get_readme_config(file: Path) -> str:
     query = "(code_fence_content) @content"
     code_blocks = ts_query(file, query, "content")
-    query_code_blocks = [code for code in code_blocks if "query" in code]
-    assert len(query_code_blocks) == 1
-    return query_code_blocks[0]
+    code_blocks = [code for code in code_blocks if "enabled" in code]
+    assert len(code_blocks) == 1
+    return code_blocks[0]
 
 
 def ts_query(file: Path, query_string: str, target: str) -> list[str]: